This invention relates generally to semiconductor integrated circuit packages, and more particularly the invention relates to a premolded tape ball grid array package having high power dissipating capabilities.
The semiconductor integrated circuit chip must be mounted and sealed on a supporting substrate with the substrate providing interconnect electrical leads for supplying electrical signals and voltages to and from the integrated circuit. The ball grid array package is presently used for housing and interconnecting large scale integrated circuits. See copending application Ser. No. 08/625,641 filed Mar. 29, 1996, incorporated herein by reference. Typically, the substrate is a rigid ceramic, for example, which includes metal lead patterns to which the chip contacts are wire bonded. Laminated substrates having multiple metal layers have been used as well as rigid tape substrates. Tape automated bonding (TAB) is typically used with the rigid tape substrates. Solder balls are used to interconnect the substrate leads to electrical contacts on a motherboard on which the substrate is mounted as a component in a larger circuit or system.
The two generic constructions for ball grid array packages are die up and die down configurations. In the die up configuration, the chip is attached to the top surface of the substrate and the balls are attached to the bottom face. In the die down configuration, the chip and balls are on the same surface of the substrate. In the die up configuration, the substrate generally has two metal layers, one on each surface of the substrate. Vias are formed in the substrate to interconnect the two metal layers.
The ceramic and laminate substrates are costly to manufacture. In most substrates, there are two or more layers of metal in the substrate which are connected by vias drilled in the substrates. This results in costly substrates. The die up configuration has greater thermal resistance, thus resulting in lower heat dissipation. This limits the power of the chip that can go into the package. With a standard plain or laminate, the bond pads and balls are on the same level, which limits the height of the bonds and thus the density of the package. Further, laminate and ceramic substrates are limited in the routing density which limits the separation of the balls on the package.
The present invention is directed to a ball grid array package which is economical to manufacture and provides high power heat dissipation.